The present invention relates generally to an injection device for improving the speed, accuracy, safety and effectiveness of the administration of an emergency, life-saving injection during an anaphylactic event, and more particularly, to an injection device that operates by way of sequential manual actuation, wherein movement of a needle guard in response to pressure against the injection site initiates a hypodermic injection and triggers the release of a plunger for delivering medication from a reservoir, in one continuous motion.
Anaphylactic reactions are serious and sometimes fatal reactions to allergens, most commonly caused by food, drugs, insect stings, etc. Studies suggest that food allergies are increasing world-wide. According to a study released by the CDC, food allergies increased approximately 50% between 1997 and 2011. More than 17 million Europeans have a food allergy according to the European Academy of Allergy and Clinical Immunology. The CDC has also reported that food allergies result in more than 300,000 ambulatory care visits per year among children under the age of 18.
Auto-injectors are universally recommended as first-aid treatment for anaphylaxis. In a World Allergy Organization survey conducted in 2003, auto-injectors containing 0.3 mg of epinephrine were reported to be available in 56.4% of countries, and those containing 0.15 mg of epinephrine were reported to be available in 43.6% of countries. Auto-injectors containing an infant dose were not available in any country.
There have been many studies published about the inability of auto-injectors to effectively deliver epinephrine, particularly in pediatric patients. A first disadvantage of auto injectors is the ineffectiveness to deliver the accurate amount of epinephrine during an emergency anaphylaxis. Current epinephrine auto injectors are available in two standard doses: 0.15 mg and 0.3 mg, with the 0.15 mg dose for patients 30 kg and under, and the 0.30 mg dose for patients above 30 kg. According to The Journal of Allergy and Clinical Immunology, neither of these doses is appropriate for children weighing less than 10 Kg. A 20 kg child would have a similar issue in being under dosed with the 0.15 mg dose, and overdosed with the 0.30 mg dose. An overdose or under dose during a life threatening anaphylaxis, especially for a child or patient with small body mass, could be fatal.
A second disadvantage of auto injectors is the inability to effectively deliver the medication intramuscularly using one standard needle length. A study conducted at the Phoenix Children's Hospital found that the needle on epinephrine auto-injectors is not long enough to reach the muscle in a significant number of children. Another study presented during the 2013 Annual Meeting of the American Academy of Allergy, Asthma & Immunology (AAAAI) suggested that delivering epinephrine into the muscle allows for more rapid absorption and leads to higher blood levels than if injected into the overlying fat. Considering the rising obesity rates in children, there is concern that epinephrine auto-injectors will not adequately deliver the medication in overweight children who may be experiencing anaphylaxis. Without proper treatment, anaphylaxis can be fatal, therefore it is critical that epinephrine is administered quickly and effectively.
Additional studies have found that patient groups other than children are at risk of not receiving an adequate dose of epinephrine in an anaphylactic emergency. One study published in the American Journal of Emergency Medicine found that the current epinephrine auto injector needle length is inadequate for intramuscular injection, especially among women.
One study conducted at the University of Manitoba assessed absorption of epinephrine when injected subcutaneously and intramuscularly in children. The data showed subcutaneous injections reached the mean maximum plasma concentration at a range of 5 to 120 minutes. Patients injected intramuscularly reached a mean maximum plasma concentration in 8+/−2 minutes. This study supports the conclusion that, in children, recommendations for subcutaneous epinephrine injection are based on anecdotal experience, and should be reevaluated in view of the finding of delayed epinephrine absorption when this route is used. This delay may have important clinical implications during an episode of systemic anaphylaxis. Thus, the intramuscular route of injection is preferable. According to the National Institute of Allergy and Infectious Disease, if epinephrine is not given promptly, rapid decline and death could occur within 30 to 60 minutes. These findings clearly illustrate the need for patients experiencing anaphylactic shock to receive rapid intramuscular injections of epinephrine.
A third disadvantage of auto injectors is the high cost, which particularly affects developing nations.
While vial and syringe combinations for epinephrine administration have the advantage of being economical, they are cumbersome to carry on a daily basis, time-consuming to load and administer, and most importantly, open the door to dosage errors. Patients requiring self-administration are typically not capable of loading a syringe and administering the correct dosage during an anaphylactic event.
Therefore, what is needed is an economical alternative for administering injections during an anaphylactic event that overcomes the disadvantages of prior art injectors.